An experimentally introduced population of Brassica rapa (Brassicaceae). 1. Phenotypic selection over three years following colonization of a novel environment

Abstract

Background and aims – Despite the importance of selection in driving evolution, little is known about the consistency of selection, particularly in the early stages of colonization of novel environments. This study examines the targets and consistency of selection on an experimentally introduced population of the annual plant, Brassica rapa L., in its first three years following introduction to a novel environment. Methods – Phenotypic selection analyses were conducted on a variety of traits collected during the first three years following introduction from California to New York, and the consistency of the strength and direction of selection was examined. Key results – The introduced population experienced direct selection for increased overall size and earlier flowering in 2011 and 2012, and increased height, earlier flowering, and longer duration of flowering in 2013. While the direction of selection only varied for height, inter-annual variation in the strength of selection was observed for a variety of traits, possibly due to changing weather patterns in the introduced environment. Conclusions – The results suggest that selection is dynamic and can fluctuate over time. Thus multi-year assessments of selection are useful for predicting evolutionary responses, particularly in the early stages of colonization of a novel environment.

Keywords

• natural selection
• plants
• phenotypic selection
• m